Sensor power management

ABSTRACT

A sensor power management arrangement includes a signal processing circuit configured to receive signal from a sensor, to test the signal against at least one criterion, and to pass the signal for further processing in response to the signal passing the at least one criterion. In this way, only signals that are of a sufficient importance or significance will consume the maximum amount of processing energy and through processing by later processes or circuitry. Should a signal from a sensor not be strong enough or meet other criteria, power will not be wasted in preparing that signal for provision to the microcontroller or microprocessor. Additional flexibility in the sensor power management can be realized by adjusting the criteria against which the sensor signal is compared based on a status of the sensor apparatus.

This application is a continuation of U.S. patent application Ser. No.13/433,546 filed Mar. 29, 2012, the entire content of which isincorporated by reference herein.

TECHNICAL FIELD

This invention relates generally to sensor technology, and morespecifically to controlling the power consumption of sensors.

BACKGROUND

Power consumption of electronic devices is becoming an increasinglyimportant aspect of electronic design. Reducing power consumption ofvarious electrical devices can result in cost savings, extension ofbattery life for portable devices, and address ecological andconservation concerns.

In the context of sensor based systems, various power managementtechniques are known as applied to microcontrollers, digital signalprocessors, and wireless communication systems as may be employed aspart of a larger sensor system. These known power management techniques,however, are not applied to the sensor node itself. Sensors, forexample, are required to be either “on” or “off” such that the sensor isable to detect the physical phenomenon for which the sensor is designed.For instance, a sensor configured to detect the presence of a personneeds to be on to perform that function. Further power savings may berealized should power management techniques be able to be applied to thesensor as part of the larger power management scheme for a sensornetwork.

SUMMARY

Generally speaking and pursuant to these various embodiments, anapparatus includes a sensor configured to output a signal in response todetecting a phenomenon or outside stimulus. The apparatus also includesa signal processing circuit configured to receive the signal from thesensor and to test the signal against at least one criterion and to passthe signal for further processing in response to the signal passing theat least one criterion. Much of the electrical power consumed inconnection with operation of a sensor is consumed as part of theoperation of various circuit elements in developing or processing thesensor's signal before provision of that signal to a microcontroller orother processing device of the larger sensing apparatus. Thus, powersavings can be realized by testing the sensor signal or informationrelated to the sensor signal at various points in its initial processingprior to provision to a microcontroller or processing device for thelarger sensing apparatus. In this way, only signals that are of asufficient importance or significance will consume the maximum amount ofprocessing energy and ultimately be processed by the microcontroller ormicroprocessor. Should a signal from a sensor not be strong enough ormeet other criteria, power will not be wasted in preparing that signalfor provision to the microcontroller or microprocessor.

Additional flexibility in the power management of the sensor can berealized by adjusting the criteria against which the sensor signal orinformation related to the sensor signal may be compared based on astatus of the sensor apparatus. For example, if the sensor apparatus isconnected to a continuous power supply such as wall socket, the criteriafor blocking signals from further processing may be lower such that moresignals are fully processed. If, on the other hand, the apparatus isoperating off of battery that is drained to a certain level wherebypower savings is more important, the criteria against which the sensorsignal or information related to the sensor signal can be adjusted suchthat fewer signals are fully processed, thereby saving additional power.These and other benefits may become clearer upon making a thoroughreview and study of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The above needs are at least partially met through provision of thesensor power management described in the following detailed descriptionparticularly when studied in conjunction with the drawings where:

FIG. 1 comprises a block diagram of an example sensing apparatus asconfigured in accordance with various embodiments of the invention.

FIG. 2 comprises a block diagram of an example sensing apparatus asconfigured in accordance with various embodiments of the invention.

FIG. 3 comprises a flow diagram of an example power management method asconfigured in accordance with various embodiments of the invention.

FIG. 4 comprises a flow diagram of another example power managementmethod as configured in accordance with various embodiments of theinvention.

Skilled artisans will appreciate that the elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions and/or relative positioningof some of the elements in the figures may be exaggerated relative toother elements to help improve understanding of various embodiments ofthe invention. Also, common but well understood elements that are usefulor necessary in a commercially feasible embodiment are often notdepicted to facilitate a less obstructive view of these variousembodiments. It will be further appreciated that certain actions and/orsteps may be described or depicted in a particular order of occurrencewhile those skilled in the art will understand that such specificitywith respect to sequence is not actually required. It will also beunderstood that the terms and expressions used herein have the ordinarytechnical meaning as is accorded to such terms and expressions bypersons skilled in the technical field as set forth above, except fordifferent specific meaning that has been set forth herein.

DETAILED DESCRIPTION

Referring now to the drawings, and in particular to FIG. 1, anillustrative context for operation of a power management apparatus ormethod compatible with many of these teachings will now be presented.FIG. 1 illustrates a sensor network including a sensor 110 that isconfigured to create a signal in response to sensing a physicalphenomenon. Such sensors may include motion detectors, light detectors,sound detectors, vibration sensors, and the like. In response to sensingthe physical phenomenon for which the sensor is designed to detect, thesensor 110 provides a signal to a sensor signal conditioning circuit120. The sensor signal conditioning circuit 120 takes the initial sensorsignal and processes it into a form receivable and understandable by amicrocontroller unit or digital signal processing circuit 130. Theprocessing circuit 130 processes the signal according to its programmingor design such that the signal will trigger certain actions based uponthe design and operation of the overall apparatus. For instance, in awireless setting the processing circuit 130 can control a radio 140 totransmit signals regarding the operation of the sensor 110 via anantenna 150. In this example, an energy storage and management circuit160 is configured to operate and control power management schemes foreach of the sensor signal conditioning circuit 120, the microcontrollerunit or digital signal processing circuit 130, and the radio 140. Thepower management of the microcontroller unit or digital signalprocessing circuit 130 and of the radio 140 are handled via conventionaland known means that require no further description herein. The controlof the power management for the sensor signal conditioner circuit 120 bythe energy storage management circuit 160 will be described in furtherdetail below.

The energy storage and management circuit 160 is further configured toreceive information from an energy harvest circuit 170. The energyharvest circuit 170 is configured to collect information regarding thepower status for the overall apparatus and provide that information tothe energy storage and management circuit 160, so that the energystorage and management circuit 160 can take the appropriate action withrespect to the power management of the various other circuits of thedevice.

Turning to FIG. 2, an example apparatus 200 for implementing powermanagement of sensor signals as illustrated. In this example, a sensor210 is configured to output an analog signal in response to detecting aphysical phenomenon. As discussed above, the signal is generated inresponse to any of a variety of physical phenomenon depending on thedesign and purpose of the given sensor. Such sensors and how the sensorscreate analog signals in response to physical phenomenon are well knownin the art and need no further description herein. The apparatus 200further includes a signal processing circuit 220 configured to receivethe analog signal and to test the analog signal against at least onecriterion. The signal processing circuit 220 is further configured topass for further processing information related to the analog signal inresponse to the analog signal passing the at least one criterion. Forexample, depending on how the individual circuit is set up, the analogsignal itself may be passed along to other circuitry for furtherprocessing in response to passing the at least one criterion, or inanother approach a single circuit may just continue processing theanalog signal as controlled by stored software or programming inresponse to the analog signal passing the at least one criterion. In yetanother approach, instead of passing along the analog signal itself forfurther processing, a processed version of the analog signal or, moregenerally speaking, information regarding the analog signal may bepassed for further processing in response to passing the test criterion.As indicated in FIG. 2, one or more sensors 210 may be connected to asingle signal processing circuit 220. In a sensor node network, morethan one sensor 210/signal processing circuit 220 is provided.

The signal processing circuit 220 can be configured to apply any of anumber of tests to the analog signal or information relating to thesignal before passing the signal or information regarding the signal forfurther processing. In one approach, the signal processing circuit 220includes an analog signal conditioning circuit 230 configured to receivethe analog signal and condition the analog signal to create aconditioned analog signal. The conditioning in this example may includeany type of conditioning necessary to prepare the analog signal forfurther processing by the circuitry. In this example, the signalprocessing circuit 220 includes a test circuit 235 configured to testthe conditioned analog signal against a signal criterion and to pass theconditioned analog signal for further processing. In response to theconditioned analog signal passing the signal criterion, one example testas may be applied by the test circuit 235 includes determining whetherthe conditioned analog signal is sufficiently strong compared to thebackground noise for the system to warrant further processing by thedevice although other tests are possible. Other example tests includedetermining whether the conditioned analog signal matches one or moreparticular time domain signatures, determining the frequency at whichthe conditioned analog signal crosses a zero line or other value, anddetecting and counting peaks and valleys in an analog signal window toname but a few.

In another approach, the signal processing circuit 220 includes adigital filtering circuit 240 configured to receive a signalcorresponding to the analog signal and to digitally filter the signal tocreate a digitally filtered signal. Digital filtering and conversion ofanalog signals into digital signals is well known in the art and needsno further description herein. In this approach, the signal processingcircuit 220 includes a test circuit 245 configured to test the digitallyfiltered signal against a digital signal criterion and to pass thedigitally filtered signal for further processing in response to thedigitally filtered signal passing the digital signal criterion. Oneexample of a test performed by the test circuit 245 relating to thedigitally filtered signal is to confirm that the signal has a particularfrequency or other characteristic sufficient to warrant furtherprocessing by the device although other tests are possible. Anotherexample test includes sample-rate up-conversion or down-conversion tofit the requirements of later microcontroller or circuit processing.

In yet another approach, the signal processing circuit 220 includes amicrocontroller signal analysis circuit 250 configured to receive asignal corresponding to the analog signal and to analyze the signal tocreate an analyzed signal. In this approach, the analysis performed tocreate the analyzed signal may comprise a more substitive analysis ofthe signal with respect to the type of signal being sensed by the sensor210 although other analysis is possible. In this approach, a testcircuit 255 is configured to test the analyzed signal against ananalyzed signal criterion and to pass the analyzed signal for furtherprocessing in response to the analyzed signal passing the analyzedsignal criterion. For example, the test circuit 255 in this approach mayapply certain substitive tests to the analyzed signal to make thedetermination of whether the signal or information related to the signalmay be processing further by the sensing device although other tests arepossible. Another example test includes determining whether the signalor information regarding a signal from the particular sensor 210 shouldbe transmitted in its entirety, in part, compressed, or not at all basedon information received from other sensors in communication with theapparatus 200.

In this example illustrated in FIG. 2, the signal processing circuit 220passes the information related to the analog signal to a processingdevice 260 configured to receive the information and act according toits programming or configuration in response to the information. Invarious embodiments, the processing device 260 may be a controller, astate processing device, or a packet processing device depending on theconfiguration of the overall apparatus 200. The processing device 260,in this example, is in communication with a radio 270 to send andreceive signals via an antenna 275. The processing device 260 is also incommunication with actuators 277 to control physical devices based uponthe overall design of the apparatus 200. Such applications of sensingdevices or networks are known in the art and need no further descriptionherein.

By one approach, the apparatus 200 can be configured such that thecriterion against which the analog signal or information related to theanalog signal is compared or tested can be variable to provideadditional flexibility for the design and application of the apparatus200. In one example for providing this flexibility, a power managementunit circuit 280 is in communication with the signal processing circuit200. In this example, the power management unit circuit 280 isconfigured to adjust the at least one criterion in response to a changein electrical power supply condition for the apparatus 200. Forinstance, the power management unit circuit 280 can be configured toreceive information relating to the electrical power supply conditionfor the apparatus such as from the processing device 260. Theinformation relating to the electrical power supply condition caninclude, for example, one or more of the type of power source being usedby the apparatus 200, the power available from the power source 200, amaximum power draw available from the power source 200, an approximatetime left before the power source becomes unavailable for the apparatus200, or the like.

In another example, the power management unit circuit 280 is configuredto adjust the at least one criterion in response to a feedback signalindicating a priority of signals to be passed for further processing.The power management unit circuit 280 in the illustrated examplereceives the feedback signal indicating the priority of signals to bepassed for further processing from the processing device 260. In thiscase, the feedback signal is used by the power management unit circuit280 to directly control the criterion based on feedback signal. Forinstance, the feedback signal can provide a specific direction withrespect to each criterion as based on a given programming or operationalenvironment as may be programmed into the processing device 260. By oneexample, the processing device 260 may note that a particular signalfrom the sensor 210 indicates a situation of interest such that it isworth operating the sensor 210 in a high power usage mode to obtain anincreased amount of signals from the sensor 210 in view of the signal ofinterest. In that situation, the processing device 260 will send afeedback signal to the power management unit circuit 280 to adjust thetest criteria to allow more signals from the sensor 210 to be fullyprocessed. For example, a motion sensor may operate at a low power(i.e., fewer signals being processed) mode until a large indication ofmotion is sensed, at which time the motion sensor may be changed to ahigh power (i.e., more signals being processed) mode to obtain finerdetails regarding the sensed movement. In another example, theprocessing device 260 can receive signals with information regarding theactivity of other sensors, and if another sensor node registeredsignificant activity, in response the processing device 260 can send afeedback signal to the power management unit circuit 280 to cause thepower management unit circuit 280 to allow more or all signals from thesensor 210 to be fully processed in view of the other sensor activity.In still another example, the processor circuit 260 is configured tomonitor the signals or information regarding the signals from the sensor210 and determine that a particular signal or signal pattern is merelybackground noise. In this case, the particular signal or signal patterncan be dismissed to limit energy waste processing background signals.

The power management unit circuit 280 can be configured to executeeither or both of the above processes (control based on informationregarding the power supply and/or control based on a feedback signal)depending on the application. For example, in a multi-modal setting(including multiple sensors), the power management unit circuit 280 canbe configured to fully power down one or more of the sensors, or fullyactivate some or all of the sensors, according to the informationregarding the power supply and or the feedback signal depending on thepower and sensor sensitivity needs at a given time. In a sensor nodenetwork with more than one sensor or signal processing circuit, onepower management unit circuit 280 can communicate with multiple sensorsand signal processing circuits or each signal processing circuit canhave a dedicated power management unit circuit 280.

Those skilled in the art will recognize and appreciate that such aprocessor devices such as the signal processing circuit 220 (includingthe circuits described therein), the processing circuit 260, and thepower management unit circuit 280 can comprise fixed-purpose hard-wiredplatforms or can comprise partially or wholly programmable platforms.All of these architectural options are well known and understood in theart and require no further description here. Those skilled in the artwill further recognize and understand that such circuits may becomprised of a plurality of physically distinct elements as is suggestedby the illustration shown in FIG. 2. It is also possible, however, toview this illustration as comprising a logical view, in which case oneor more of these elements can be enabled and realized via a sharedplatform. It will also be understood that such a shared platform maycomprise a wholly or at least partially programmable platform as areknown in the art. In another design option, the test circuits 235, 245,and 255 may include one of the group consisting of low-complexity energydetectors, max/min comparators, low-complexity filter banks, andcombinations thereof.

In an additional alternative embodiment, the functionality or logicdescribed in FIG. 2 may be embodied in the form of code that may beexecuted in a distinct processor circuit. If embodied in software, eachblock may represent a module, segment, or portion of code that comprisesprogram instructions to implement the specified logical function(s). Theprogram instructions may be embodied in the form of source code thatcomprises human-readable statements written in a programming language ormachine code that comprises numerical instructions recognizable by asuitable execution system such as a processor in a computer system orother system. The machine code may be converted from the source code,etc. If embodied in hardware, each block may represent a circuit or anumber of interconnected circuits to implement the specified logicalfunction(s).

Turning now to FIG. 3, an illustrative process that is compatible withmany of these teachings will now be presented. The method includesreceiving 310 an analog signal from a sensor configured to output theanalog signal in response to detecting a physical phenomenon. The methodfurther includes testing 320 by a signal processing circuit the analogsignal against at least one criterion. Information related to the analogsignal is passed 330 for further processing by other circuitry inresponse to the analog signal passing the at least one criterion.Optionally, the method may include modifying 340 the at least onecriterion in response to a change in an electrical power supplycondition for the other circuitry and/or modifying 350 the at least onecriterion in response to receiving a feedback signal indicating apriority of signals to be passed for further processing as describedherein.

The steps of testing 320 the signal and passing 330 the signal forfurther processing in response to passing the criterion during thetesting 320 can be performed in any number of ways. With reference toFIG. 4, one example process for testing and passing a signal orinformation regarding a signal from a sensor will be described. One ofskill in the art will recognize that although the flow chart of FIG. 4shows a specific order of implementation, it is understood that theorder may differ from that which is depicted depending on variousfactors, such as, for example, the time it takes for various circuits tocomplete various tasks and the like. For example, the order of two ormore blocks may be scrambled relative to the order shown. Also, two ormore blocks shown in succession may be executed concurrently or withpartial concurrence. Moreover, certain blocks may be omitted altogetherdepending on the given configuration. It is understood that all suchvariations are within the scope of these teachings.

In the illustrated example, the method includes conditioning 410 theanalog signal to create a conditioned analog signal and testing 414 theconditioned analog signal against a signal criterion. The method in thisapproach includes passing 418 the conditioned analog signal for furtherprocessing in response to the conditioned analog signal passing thesignal criterion. In another aspect, the method includes digitallyfiltering 420 a signal corresponding to the analog signal to create adigitally filtered signal and testing 424 the digitally filtered signalagainst a digital signal criterion. In this case, the digitally filteredsignal is passed 428 for further processing in response to the digitallyfiltered signal passing the digital signal criterion. In still anotheraspect, the method includes analyzing 430 a signal corresponding to theanalog signal to create an analyzed signal and testing 434 the analyzedsignal against an analyzed signal criterion. Here, the analyzed signalis passed 438 for further processing in response to the analyzed signalpassing the analyzed signal criterion. Each of these various analysescan be done in view of various criteria such as those described abovewith reference to FIG. 2.

In one example, if each of the signal processing, testing, and passingsteps as described with reference to FIG. 4 were configured to worktogether in a single apparatus, the apparatus may be described asfollows. The apparatus in such an example would include, with referenceto FIG. 2, a sensor 210 configured to output an analog signal inresponse to detecting a physical phenomenon and an analog signalconditioning circuit 230 configured to receive the analog signal and tocondition the analog signal to create a conditioned analog signal. Theapparatus further includes an analog test circuit 235 configured to testthe conditioned analog signal against a signal criterion and to pass thecondition analog signal for further processing in response to theconditioned analog signal passing the signal criterion. The next portionof processing in this apparatus includes a digital filtering circuit 240configured to receive the conditioned analog signal in response to theconditioned analog signal passing the signal criterion. In this case,the digital filtering circuit 240 is configured to digitally filter theconditioned analog signal to create a digitally filtered signal. Adigital test circuit 245 is configured to test the digitally filteredsignal against a digital signal criterion and to pass the digitallyfiltered signal for further processing in response to the digitallyfiltered signal passing the digital signal criterion. In a furtherportion of the analysis, a microcontroller signal analysis circuit 250is configured to receive the digitally filtered signal and to analyzethe digitally filtered signal to create an analyzed signal. Here, ananalyzed signal test circuit 255 is configured to test the analyzedsignal against an analyzed signal criterion, and to pass the analyzedsignal for further processing in response to the analyzed signal passingthe analyzed signal criterion. The analog test circuit 235, the digitaltest circuit 245, and the analyzed signal test circuit 255 in variousapproaches may comprise one or more of the group consisting oflow-complexity energy detectors, max/min comparators, low-complexityfilter banks, and combinations thereof. Using such circuitry andapproaches, the test circuits can be configured to analyze and pass thesignals in any of a variety of ways that may be suitable to a givenapplication.

A power management unit circuit 280 is in communication with the analogtest circuit 235, the digital test circuit 245, and the analyzed signaltest circuit 255. In this configuration, the power management unitcircuit 280 is configured to adjust the signal criterion, digital signalcriterion, and analyzed signal criterion in response to a change in anelectrical power supply condition for the apparatus. In one optionalapproach, the power management unit circuit 280 is configured to receivea power supply signal indicating the electrical power supply conditionfor the apparatus. In response to receiving a power supply signalindicating a large electrical power supply for the apparatus, the powermanagement unit circuit 280 is configured to adjust the signalcriterion, the digital signal criterion, and the analyzed signalcriterion to allow more signals to pass for further processing. Inanother approach, the power management unit circuit 280 is configuredto, in response to receiving a power supply signal indicating arestricted electrical power supply to the apparatus, adjust the signalcriterion, the digital signal criterion, and the analyzed signalcriterion to allow further signals to pass for further processing,thereby conserving electrical power.

In a further aspect, the power management unit circuit 280 is configuredto receive a feedback signal indicating a priority of signals and inresponse to receiving the feedback signal to adjust the signalcriterion, the digital signal criterion, and the analyzed signalcriterion to allow certain signals to pass for further processing inaccord with the feedback signal. In this aspect, the power managementunit circuit 280 can react to feedback signals from elsewhere in thedevice with respect to how sensitive the sensor needs to be or thenumber of sensors that need to be fully activated as described above.

So configured, systems including sensor devices can have improved powermanagement controls through control of the processing of signalsgenerated by various sensors. For instance, because sensors at theirbase level usually initiate in the first instance an analog signal, ifthat initial analog signal does not pass a certain criterion, thenfurther power is not wasted by processing that signal. To furtherprocess that analog signal, for example, by turning the analog signalinto a digital signal for digital processing to thereby save energy.Additional processing steps for signals generated by sensors can then besuccessive avoided depending on the type of sensor and phenomenon beingdetected and tracked by a given system. Using the power managementtechniques described in this disclosure, not only can power savings berealized with respect to a single sensor, multi-sensor systems can alsobe manipulated to realize power savings using the same techniques.

Those skilled in the art will recognize that a wide variety ofmodifications, alterations, and combinations can be made with respect tothe above described embodiments without departing from the scope of theinvention. For instance, the sensor and sensor signal conditioningcircuit may be combined into a single housing with other circuitrylocated elsewhere. Such modifications, alterations, and combinations areto be viewed as being within the ambit of the inventive concept.

What is claimed is:
 1. An apparatus comprising: a sensor configured tooutput an analog signal responsive to detecting a physical phenomenon;an analog signal conditioning circuit coupled to the sensor, the analogsignal conditioning circuit configured to receive the analog signal andto condition the analog signal to form a conditioned analog signal; adigital filtering circuit coupled to the analog signal conditioningcircuit, the digital filtering circuit configured to receive theconditioned analog signal responsive to the conditioned analog signalpassing a signal criterion and to digitally filter the conditionedanalog signal to form a digitally filtered signal; a microcontrollersignal analysis circuit coupled to the digital filtering circuit, themicrocontroller signal analysis circuit configured to receive thedigitally filtered signal and to analyze the digitally filtered signalto form an analyzed signal; and a power management unit circuit coupledto the digital filtering circuit, the power management unit circuitconfigured to adjust the signal criterion to increase a number ofinstances of the conditioned analog signal that pass the signalcriterion, responsive to the analyzed signal indicating a signalcondition of interest from the sensor.
 2. The apparatus of claim 1,wherein the power management unit circuit is configured to: receive apower supply signal indicating an unrestricted electrical power supplycondition or a restricted electrical power supply condition; responsiveto the power supply signal indicating the unrestricted electrical powersupply condition, adjust the signal criterion to increase the number ofinstances of the conditioned analog signal that pass the signalcriterion; and responsive to the power supply signal indicating therestricted electrical power supply condition, adjust the signalcriterion to reduce the number of instances of the conditioned analogsignal that pass the signal criterion.
 3. The apparatus of claim 1,wherein the power management unit circuit is configured to: receive afeedback signal indicating a priority of signals; and responsive to thefeedback signal, adjust the signal criterion to allow only a subset ofinstances of the conditioned analog signal to pass the signal criterion.